diff --git a/inc/instance-config.php b/inc/instance-config.php
index 5a2837d5..90192586 100644
--- a/inc/instance-config.php
+++ b/inc/instance-config.php
@@ -133,6 +133,9 @@ $config['max_filesize'] = 50 * 1024 * 1024; // 50MB
 $config['webm']['allow_audio'] = true;
 $config['webm']['max_length'] = 1000;
 
+$config['pdf_file_thumbnail'] = true;
+$config['djvu_file_thumbnail'] = true;
+
 // Allowed image file extensions.
 $config['allowed_ext'][] = 'jpg';
 $config['allowed_ext'][] = 'jpeg';
diff --git a/js/inline-expanding.js b/js/inline-expanding.js
index 5db95c09..8a6c6a1b 100644
--- a/js/inline-expanding.js
+++ b/js/inline-expanding.js
@@ -100,7 +100,8 @@ $(document).ready(function(){
 
 		for (var i = 0; i < link.length; i++) {
 			if (typeof link[i] == "object" && link[i].childNodes && typeof link[i].childNodes[0] !== 'undefined' &&
-					link[i].childNodes[0].src && link[i].childNodes[0].className.match(/post-image/) && !link[i].className.match(/file/)) {
+					link[i].childNodes[0].src && link[i].childNodes[0].className.match(/post-image/) && !link[i].className.match(/file/) &&
+                    !link[i].href.match("\\.(pdf|djvu|djv)$") ) {
 				link[i].onclick = function(e) {
 					var img, post_body, still_open, canvas, scroll;
 					var thumb = this.childNodes[0];